If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up
process will only take up about a minute of two of your time.

Air bubbles coming from carb?????? HELP????

Ok im new to the rc world and i just purchased the avalanche xtr with the sh .28 engine. Well ive figured out a lot about it im a mechanic so i love to tinker with things like this. Well it starts very good and even runs good until it gets hot then air bubbles start coming out of the carb into the fuel line keeping it from being able to prime. Ive replaced tank, and lines there is no fuel filter or primer bowl. I have tried richening it and leaning it i think the temp is getting over 300 degrees but i can not understand why.im running artic rc 20% nitro 9% oil im not sure if its boiling the fuel but the carb is only around 120 degrees when the bubbles start. Ive checked the engine for leaks and the only thing i can find is very few air bubbles coming from around the flywheel but from what i have researched online is that is going to happen and its ok as long as its not leaking fuel which its not. Any help would be very appreciated im probably 200 miles from a hobby shop and im probably the only one in my area with a rc car and im out of things to try. Thanks

RE: Air bubbles coming from carb?????? HELP????

I'm not extremely experienced in the hobby (only 3 years) but in my past experiances when the carb itself is pushing air out into the fuel line, then your running too hot, causing the engine to shut off and the carb to act the way it is, richen it up and you should be ok

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: Shady9503

I'm not extremely experienced in the hobby (only 3 years) but in my past experiances when the carb itself is pushing air out into the fuel line, then your running too hot, causing the engine to shut off and the carb to act the way it is, richen it up and you should be ok

+1 on this. Definitely getting too hot, when you see the bubbles they are probably pushing back to the tank and you'll hear the fuel boiling in the engine. Definitely re-tune.

RE: Air bubbles coming from carb?????? HELP????

well thats what i thought and i have richened and richened LSN and HSN i have lots of smoke i can even richen it until its spitting raw fuel out the exhaust and it still doesnt cool down has anyone had any experience with the artic rc fuel? im starting to believe thats the problem but its 20%nitro and 4.5 synthetic oil and 4.5% castor. is 9% oil enough? and also does the idle jet have anything to do with the temp? And thanks again for you guys response its good to know there is someone willing to help

RE: Air bubbles coming from carb?????? HELP????

Could be your fuel but i doubt it, i use O'donnells 20% nitro with 8% oil although fuel quality does matter to a point, i suspect its tuning, try going back to stock and re tuning, also the idle set screw should be set so that when idling the gap is only 1-2mm were always willing to help

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

well thats what i thought and i haveΒ*richened and richened LSN and HSN i have lots of smoke i can even richen it until its spitting raw fuel out the exhaust and it still doesnt cool down has anyone had any experience with the artic rc fuel? im starting to believe thats the problem but its 20%nitro and 4.5 synthetic oil and 4.5% castor. is 9% oil enough? and also does the idle jet have anything to do with the temp? And thanks again for you guys response its good to know there is someone willing to help

it is possible the engine is cooked. I've seen more than one nitro engine respond this way. I've worked on a few with precisely this problem. The engine will start and run perfect until it warms up, then the fuel starts to boil and finally it will stall and not restart until it cools down. You can richen up the needles all you want but it still overheats. If this is whats happening, you can first try sealing your engine and making sure your just not the victim of an air leak. Also your LSN can really help facilitate this problem if its too lean.

RE: Air bubbles coming from carb?????? HELP????

# 6 Ive been checking out new engines anyways since i didnt get to break this one in myself and im sure the guy before me had no clue what he was doing. Should i go back with the sh .28? and im not sure how to seal the engine? do you mean relpace all the bearings or is there something else you can do to seal it. I've stopped up intake and exhaust and blew into the fuel line with all my might and the only bubbles i see are coming between the flywheel and the block and its very very few bubbles. Is this normal?

# 5 I just tuned back to stock i will try again tomorrow and also i just bought some o donnels fuel so im gonna try the fuel, sealing the engine and a little more tunning before i replace it

RE: Air bubbles coming from carb?????? HELP????

and also on my assembly guide i cant find the part number for the bolts that go through the chassis and hold the diff housing on on either one of the 3 diffs they are the same but it does not show it on the breakdown. could someone explain to me how they measure the bolts. The way it describes it is 3*8 and im not sure how to interpret that. ha thanks

RE: Air bubbles coming from carb?????? HELP????

To seal the engine, you remove the pullstart and carb. Use silicone sealer like you would on valve cover gaskets. Also make sure your exhaust gasket is good, and your cooling head is tight at the block. I would replace it with the same engine. They're very good for bashing around. The sky is the limit if you want to spend more, but you can probably find a replacement from a new tear down on eBay for around $120.

RE: Air bubbles coming from carb?????? HELP????

will i got it back out today and i can finally keep the temp around 250 if i keep it so rich it hardly has any power. half throttle is not so bad its when i run it hard is when it wants to get to over 300. I obviously have internal engine problems i just cant see how when the engine has only had about 3 quarts of fuel through it. Is buying just the piston and sleeve worth saving the 50 bucks on vs buying the complete engine.

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

will i got it back out today and i can finally keep the temp around 250 if i keep it so rich it hardly has any power. half throttle is not so bad its when i run it hard is when it wants to get toΒ*over 300. I obviously have internal engine problems i just cant see how when the engine has only had about 3 quarts of fuel through it. Is buying justΒ*the piston and sleeve worth saving the 50 bucks on vs buying the complete engine.

It really depends on how you look at it. If your new to the hobby, buying a complete engine isn't a bad idea since it will come complete. I'm referring to buying an engine from a new teardown. These commonly come complete with clutch bell and flywheel, exhaust, pullstart and carb. Then you have all the old parts on your old engine if you need any as spares later.

RE: Air bubbles coming from carb?????? HELP????

well now i think im in trouble i took apart the engine just to check for visual damage and everything looked perfect but im a beginner on nitro engines. welll i cleaned everything up and put it back together and now it has unreal compression not sure what i did but it does run or at least crank but its late here and i will try it tomorrow and see if i did something wrong. Anyone ever ran into this? and all i took off was back plate where pull start is and the cooling head. I did not remove the piston and sleeve

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

well now i think im in trouble i took apart the engine just to check for visual damage and everything looked perfect but im a beginner on nitro engines. welll i cleaned everything up and put it back together and now it has unreal compression not sure what i did but it does run or at least crank but its late here and i will try it tomorrow and see if i did something wrong. Anyone ever ran into this? and all i took off was back plate where pull start is and the cooling head. I did not remove the piston and sleeve

When you say it has unreal compression, do you mean its just very hard to turn over? You can put the one way bearing plate on so that it's in a bind with the crankshaft if it's not perfect. I've seen this before with this engine, the back plate looks like its going on straight, but it hasn't really slid into the crank properly.

RE: Air bubbles coming from carb?????? HELP????

well it doesnt feel like anythings binding cause if i take glow plug out it turns easy but im definately gonna tear it back apart to make sure thats not the case i just do not remember it being that hard to turn over before and the little plate that connects to the crankshaft does it matter which spot i connect it to?i thought i connected it to the one it was on cause it was scarred a little but im not 100 % sure.

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

well it doesnt feel like anythings binding cause if i take glow plug out it turns easyΒ*but im definately gonna tear it back apart to make sure thats not the case i just do not remember it being that hard to turn over beforeΒ*and the little plate that connects to the crankshaft does it matter which spot i connect it to?i thought i connected it to the one it was on cause it was scarred a little but im not 100 % sure.

If it turns over fine without the glow plug then your probably correct, it's just the compression. These engines can be very difficult to turn over especially if your just holding it in your hand.

RE: Air bubbles coming from carb?????? HELP????

ok i tore the engine back apart completely and cleaned everything and put it back together. ITS STILL RUNNING HOT. Im jus having trouble understanding what the problem is to make it run hot when everything looks fine. Im not doubting you at all cause im not familiar with them at all but im just curious. What are some things to check for? and also where is a good website to find a new sh .28 engine for the best price?

RE: Air bubbles coming from carb?????? HELP????

You can get a new engine for relatively cheap on ebay if your looking for a new engine, around 120$ maybe even less. stock the engines come with medium plugs, OS #8 should be fine
in terms of it running hot, it might be like dads said, you may simply have a cooked engine.

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

ok i tore the engine back apart completely and cleaned everything and put it back together. ITS STILL RUNNING HOT. Im jus having trouble understanding what the problem is to make it run hot when everything looks fine. Im not doubting you at all cause im not familiar with them at all but im just curious. What are some things to check for? and also where is a good website to find a new sh .28 engine for the best price?

I wish I could be more specific but I've seen this exact problem before on a friend's savage, almost identical engine. It would start, idle, and run perfect. Was running plenty rich but once you got close to half a tank it would just overheat for no apparent reason. We took it apart, couldn't find anything wrong with it. I sealed everything you could imagine, but it didn't help. Tried using a different carb, same thing. He wound up replacing it, we never could figure out what was wrong. The problem points to an air leak somewhere, but we never found it. As far as replacements go, the least expensive is usually eBay. I found a new engine from an avalanche from a new teardown that was complete with engine mounts, header and pipe, carb, flywheel, clutch bell and pullstart for$120 with free shipping for another truck I was rebuilding, but I just checked eBay and right now there were no good deals to speak of. You might have to wait a few days for someone to put up some new inventory. To me, for that price I'd wait until one comes up. If I see one post I'll send you a link.

RE: Air bubbles coming from carb?????? HELP????

Well im at the point where im ready to purchase one plus like you said ill be glad i have all the extra parts anyways. Thanks for your help cause i am clueless without you guys, and if you happen to find one please let me know and ill keep checking and ebay is where i have purchased all my other parts for it so ill keep checking too but in the meantime im gonna keep running it till it blows up. or it melts the piston

RE: Air bubbles coming from carb?????? HELP????

ORIGINAL: justinteoc1

Well im at the point where im ready to purchase one plus like you said ill be glad i have all the extra parts anyways. Thanks for your help cause i am clueless without you guys, and if you happen to find one please Β*let me know and ill keep checking and ebay is where i have purchased all my other parts for it so ill keep checking too but in the meantime im gonna keep running it till it blows up. or it melts the piston

You should look into redcats engine exchange program. I think they'll replace your engine for half of retail if you send the old one back. They're listing the .28 for $180 so I guess it would be $90 plus shipping both ways.

RE: Air bubbles coming from carb?????? HELP????

+1 on the Exchange program, good deal on a new engine, espcially on the sh.28 good basher engine

ORIGINAL: Dads like rc too

ORIGINAL: justinteoc1

Well im at the point where im ready to purchase one plus like you said ill be glad i have all the extra parts anyways. Thanks for your help cause i am clueless without you guys, and if you happen to find one please let me know and ill keep checking and ebay is where i have purchased all my other parts for it so ill keep checking too but in the meantime im gonna keep running it till it blows up. or it melts the piston

You should look into redcats engine exchange program. I think they'll replace your engine for half of retail if you send the old one back. They're listing the .28 for $180 so I guess it would be $90 plus shipping both ways.

RE: Air bubbles coming from carb?????? HELP????

I see there is several sh 28 engines for sale on ebay that are from outside the country has anyone had any experience with buying something out of the country the guy has good feedback but i just wanted a second opinion and im not really worried about the ship time it will give me time to get the drivetrain in great condition.
Also is there a way to measure the pinch of a piston and sleeve i removed mine and when its cold it will not push out the top of the sleeve but it is about 1/16 of an inch from being flush with the sleeve. Is this normal or should it not go that far. Im just curious about when its hot cause when it gets hot the engine becomes very easy to turn over